Multiple gaseous discharge display/memory panel having thin film dielectric charge storage member

ABSTRACT

There is disclosed a multiple gaseous discharge display/memory panel having an electrical memory and capable of producing a visual display, the panel being characterized by an ionizable gaseous medium in a gas chamber formed by a pair of opposed charge storage members which are respectively backed by a series of parallel-like conductor (electrode) members, the conductor members behind each charge storage member being transversely oriented with respect to the conductor members behind the opposing charge storage member so as to define a plurality of discrete discharge volumes constituting a discharge unit, each charge storage member being comprised of a continuous thin film of dielectric material having a thickness of 150,000 angstrom units or less.

Ilnite Ettes Hoehn et a1.

tent [191 [75] Inventors: Harold J Hoehn, Toledo; Roger E. Ernsthausen,Lackey, both of Ohio [73] Assignee: Owens-Illinois, Inc, Toledo, Ohio[22] Filed: Oct. 29, 1974 [21] Appl. No.: 518,421

Related US. Application Data [60] Division of Ser No. 399,548, Sept. 21,1973 Pat. No. 3.852.607. which is a continuation-in-part of Ser. No.146.796, May 25, 1971. abandoned.

11/1971 Berthold et all. 313/221 3.634.719 1/1972 Ernsthausen 313/221 X3.846.671) 11/1974 Schaufele 315/169 TV Primary E.\'umi/zerJames W.Lawrence Assistant E.\'an1l'nerE. R. LaRoche Attorney, Agent, orFirm-Donald Keith Wedding [57] ABSTRACT There is disclosed a multiplegaseous discharge display/memory panel having an electrical memory andcapable of producing a visual display, the panel being characterized byan ionizable gaseous medium in a gas chamber formed by a pair of opposedcharge storage members which are respectively backed by a series ofparallel-like conductor (electrode) members. the conductor membersbehind each charge storage member being transversely oriented withrespect to the conductor members behind the opposing charge storagemember so as to define a plurality of discrete discharge volumesconstituting a discharge unit. each charge storage member beingcomprised of a continu ous thin film of dielectric material having athickness of 150,000 angstrom units or less.

1 Claim, 7 Drawing Figures US. Patent Nov. 11,1975 Sheetlof3 3,919,577

US. Patent Nov. 11, 1975 Sheet3of3 3,919,577

ESY

MULTIPLE GASEOUS DISCHARGE DISPLAY/MEMORY PANEL HAVING THIN FILMDIELECTRIC CHARGE STORAGE MEMBER RELATED APPLICATIONS This is adivisional application'of copending U.S. Pat. application Ser. No.399,548, filed Sept. 21, 1973, now U.S. Pat. No. 3,852,607, which is acontinuation-inpart of copending U.S. Pat. application Ser. No. 146,796,filed May 25, 1971, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to novel multiple gasdischarge display/memory panels which have an electrical memory andwhich are capable of producing a visual display or representation ofdata such as numerals, letters, television display, radar displays,binary words, etc.

Multiple gas discharge display and/or memory panels of one particulartype with which the present invention is concerned are characterized byan ionizable gaseous medium, usually a mixture of at least two gases atan appropriate gas pressure, in a thin gas chamber or space between apair of opposed dielectric charge storage members which are backed byconductor (electrode) members, the conductor members backing eachdielectric member typically being appropriately oriented so as to definea plurality of discrete gas discharge units or cells.

In some prior art panels the discharge cells are additionally defined bysurrounding or confining physical structure such as apertures inperforated glass plates and the like so as to be physically isolatedrelative to other cells. In either case, with or without the confiningphysical structure, charges (electrons, ions) produced upon ionizationof the elemental gas volume of a selected discharge cell, when properalternating operating potentials are applied to selected conductorsthereof, are collected upon the surfaces of the dielectric atspecifically defined locations and constitute an electrical fieldopposing the electrical field which created them so as to terminate thedischarge for the remainder of the half cycle and aid in the initiationof a discharge on a succedding opposite half cycle of applied voltage,such charges as are stored constituting an electrical memory.

Thus, the dielectric layers prevent the passage of substantialconductive current from the conductor members to the gaseous medium andalso serve as collecting surfaces for ionized gaseous medium charges(electrons, ions) during the alternate half cycles of the AC. operatingpotentials, such charges collecting first on one elemental or discretedielectric surface area and then on an opposing elemental or discretedielectric surface area on alternate half cycles to constitute anelectrical memory.

An example of a panel structure containing nonphysically isolated oropen discharge cells is disclosed in U.S. letters Pat. No. 3,499,167issued to Theodore C. Baker, et al.

An example of a panel containing physically isolated cells is disclosedin the article by D. L. Bitzer and H. G. Slottow entitled The PlasmaDisplay Panel A Digitally Addressable Display With Inherent Memory,Proceeding of the Fall Joint Computer Conference, IEEE, San Francisco,California, Nov. 1966, pages 541-547. Also reference is made to U.S.letters Pat.

In the construction of the panel, a continuous volume of ionizablegas isconfined between a pair of dielectric surfaces backed by conductorarrays typically forming matrix elements. The cross conductor arrays maybe orthogonally related (but any other configuration of conductor arraysmay be used) to define a plurality of opposed pairs of charge storageareas on the surfaces of the dielectric boudning or confining the gas.Thus, for a conductor matrix having H rows and C columns the number ofelemental or discrete areas will be twice the number of such elementaldischarge cells.

In addition, the panel may comprise a so-called monolithic structure inwhich the conductor arrays are created on a single substrate and whereintwo or more arrays are separated from each other and from the gaseousmedium by at least one insulating member. In such a device the gasdischarge takes place not between two opposing electrodes, but betweentwo contiguous or adjacent electrodes on the same substrate; the gasbeing confined between the substrate and an outer retaining wall.

It is also feasible to have a gas discharge device wherein some of theconductive or electrode members are in direct contact with the gaseousmedium and the remaining electrode members are appropriately insulatedfrom such gas, i.e., at least one insulated electrode.

In addition to the matrix configuration, the conductor arrays may beshaped otherwise. Accordingly, while the preferred conductor arrangementis of the crossed grid type as discussed herein, it is likewise apparentthat where a maximal variety of two dimensional display patterns is notnecessary, as where specific standardized visual shapes (e.g., numerals,letters, words, etc.) are to be formed and image resolution is notcritical, the conductors may be shaped accordingly, i.e., a segmenteddisplay.

The gas is one which produces visible light or invisible radiation whichstimulates a phosphor (if visual display is an objective) and a copioussupply of charges (ions and electrons) during discharge.

In the prior art, a wide variety of gases and gas mixtures have beenutilized as the gaseous medium in a number of different gas dischargedevices. Typical of such gases include pure gases and mixtures of C0; C0halogens; nitrogen; NH oxygen, water vapor; hydrogen hydrocarbons; P Oboron fluoride, acid fumes; TiCl air; H 0 vapors of sodium, mercury,thalium, cadmium, rubidium, and cesium; carbon disulfide, laughing gas;H S; deoxygenalted air; phosphorus vapors; C H CH naphthalene vapor;anthracene; freon, ethyl alcohol; methylene bromide; heavy hydrogen;electron attaching gases; sulfur hexafluoride; tritium; radioactivegases; and the so-called rare or inert Group VIII gases.

In an open cell Baker, et al. type panel, the gas pressure and theelectric field are sufficient to laterally confine charges generated ondischarge within elemental or discrete dielectric areas within theperimeter of such areas, especially in a panel containing non-isolateddischarge cells. As described in the Baker, et al. patent, the spacebetween the dielectric surfaces occupied by the gas is such as to permitphotons generated on discharge in a selected discrete or elementalvolume of gas to pass freely through the gas space and strike surfaceareas of dielectric remote from the selected discrete volumes, suchremote, photon struck dielectric surface areas thereby emittingelectrons so as to condition at 3 least one elemental volume other thanthe elemental volume in which the photons originated.

With respect to the memory function of a given discharge panel, theallowable distance or spacing between the dielectric surfaces depends,inter alia, on the frequency of the alternating current supply, thedistance typically being greater for lower frequencies.

While the prior art does disclosed gaseous discharge devices havingexternally positioned electrodes for initiating a gaseous discharge,sometimes called electrodeless discharge, such prior art devicesutilized frequencies and spacing or discharge volumes and operatingpressures such that although discharges are initiated in the gaseousmedium, such discharges are ineffective or not utilized for chargegeneration and storage at higher frequencies; although charge storagemay be realized at lower frequencies, such charge storage has not beenutilized in a display/memory device in the manner of the Bitzer-Slottowor Baker, et al. invention.

The term memory margin is defined herein as V,V,; M. M. V 1/2 where V,isthe half amplitude of the smallest sustaining voltage signal whichresults in a discharge every half cycle, but at which the cell is notbi-stable and V is the half amplitude of the minimum applied voltagesufficient to sustain discharges once initiated.

It will be understood that the basic electrical phenomenon utilized inthis invention is the generation of charges (ions and electrons)alternately storable at pairs of opposed or facing discrete points orareas on a pair of dielectric surfaces backed by conductors connected toa source of operating potential. Such stored charges result in anelectrical field opposing the field produced by the applied potentialthat created them and hence operate to terminate ionization in theelemental gas volume between opposed or facing discrete points or areasof dielectric surface. The term sustain a discharge means producing asequence of momentary discharges, at least one discharge for each halfcycle of applied alternating sustaining voltage, once the elemental gasvolume has been fired, to maintain alternate storing of charges at pairsof opposed discrete areas on the dielectric surfaces.

As used herein, a cell is in the ion state when a quantity of charge isstored in the cell such that on each half cycle of the sustainingvoltage, a gaseousdischarge is produced.

In addition to the sustaining voltage, other voltages may be utilized tooperate the panel, such as firing, addressing, and writing voltages.

A firing voltage" is any voltage, regardless of source, required todischarge a cell. Such voltage may be completely external in origin ormay be comprised of internal cell wall voltage in combination withexternally originated voltages.

An addressing voltage is a voltage produced on the panel X Y electrodecoordinates such that at the selected cell or cells, the total voltageapplied across the cell is equal to or greater than the firing voltagewhereby the cell is discharged.

A writing voltage is an addressing voltage of sufficient magnitude tomake it probable that on subsequent sustaining voltage half cycles, thecell will be in the on state.

In the operation of a multiple gaseous discharge device of the typedescribed hereinbefore, it is necessary to condition the discreteelemental gas volume of each discharge cell by supplying at least onefree electron thereto such that a gaseous discharge can be initiatedwhen the cell is addressed with an appropriate voltage signal.

The prior art has disclosed and practiced various means for conditioninggaseous discharge cells.

One such means of panel conditioning comprises a socalled electronicprocess whereby an electronic conditioning signal or pulse isperiodically applied to all of the panel discharge cells, as disclosedfor example in British Pat. specification No. 1,161,832, page 8, lines56 to 76. Reference is also made to US. letters Pat. No. 3,559,190 andThe Device Characteristics of the Plasma Display Element by Johnson, etal., IEEE Transactions On Electron Devices, September, 1971. However,electronic conditioning is self-conditioning and is only effective aftera discharge cell has been previously conditioned; that is, electronicconditioning involves periodically discharging a cell and is therefore away of maintaining the presence of free electrons. Accordingly, onecannot wait too long between the periodically applied conditioningpulses since there must be at least one free electron present in orderto discharge and condition a cell.

Another conditioning method comprises the use of external radiation,such as flooding part or all of the gaseous medium of the panel withultraviolet radiation. This external conditioning method has the obviousdisadvantage that it is not always convenient or possible to provideexternal radiation to a panel, especially if the panel is in a remoteposition. Likewise, an external UV source requires auxiliary equipment.Accordingly, the use of internal conditioning is generally preferred.

One internal conditioning means comprises using internal radiation, suchas by the inclusion of a radioactive material.

Another means of internal conditioning, which we call photonconditioning, comprises using one or more so-called pilot dischargecells in the on-state for the generation of photons. This isparticularly effective in a so-called open cell construction (asdescribed in the Baker, et al. patent) wherein the space between thedielectric surfaces occupied by the gas is such as to permit photonsgenerated on discharge in a selected discrete or elemental volume of gas(discharge cell) to pass freely through the panel gas space so as tocondition other and more remote elemental volumes of other dischargeunits. In addition to or in lieu of the pilot cells, one may use othersources of photons internal to the panel.

Internal photon conditioning may be unreliable when a given dischargeunit to be addressed is remote in distance relative to the conditioningsource, e.g., the pilot cell. Accordingly, a multiplicity of pilot cellsmay be required for the conditioning of a panel having a large geometricarea. In one highly convenient arrangement, the panel matrix border(perimeter) is comprised of a plurality of such pilot cells.

DRAWINGS ILLUSTRATING GAS DISCHARGE DISPLAY/MEMORY PANEL Reference ismade to the accompanying drawings and the hereinafter discussed FIGS. 1to 7 shown thereon illustrating a gas discharge display/memory panel ofthe Baker, et al. type.

FIG. 1 is a partially cut-away plan view of a gaseous dischargedisplay/memory panel as connected to a diagrammatically illustratedsource of operating potentials.

FIG. 2 is a cross-sectional view (enlarged, but not to proportionalscale since the thickness of the gas volume, dielectric members andconductor arrays have been enlarged for purposes of illustration) takenon lines 2 2 of FIG. 1.

FIG. 3 is an explanatory partial cross-sectional view similar to FIG. 2(enlarged, but not to proportional scale).

FIG. 4 is an isometric view of a gaseous discharge display/memory panel.

FlGS. 5, 6, and 7 are partial cross-sectional views illustrating threedifferent embodiments of this invention.

The invention utilizes a pair of dielectric films 10 and 11 separated bya thin layer or volume ofa gaseous discharge medium 12, the medium 12producing a copious supply of charges (ions and electrons) which arealternately collectable on the surfaces of the dielectric members atopposed or facing elemental or discrete areas X and Y defined by theconductor matrix on nongas-contacting sides of the dielectric members,each dielectric member presenting large open surface areas and aplurality of pairs of elemental X and Y area. While the electricallyoperative structural members such as the dielectric members 10 and 11and conductor matrixes l3 and 14 are all relatively thin (beingexaggerated in thickness in the drawings) they are formed on andsupported by rigid nonconductive support members 16 and 17 respectively.

Preferably, one or both of nonconductive support members 16 and 17 passlight produced by discharge in the elemental gas volumes. Preferably,they are transparent glass members and these members essentially definethe overall thickness and strength of the panel. For example, thethickness of gas layer 12 as determined by spacer 15 is usually under 10mils and preferably about 4 to 8 mils, dielectric layers 10 and 11 (overthe conductors at the elemental or discrete X and Y areas) are usuallybetween 1 and 2 mils thick, and conductors l3 and 14 about8,000angstroms thick. However, support members 16 and 17 are muchthicker (particularly in larger panels) so as to provide as muchruggedness as may be desired to compensate for stresses in the panel.Support members 16 and 17 also serve as heat sinks for heat generated bydischarges and thus minimize the effect of temperature on operation ofthe device. If it is desired that only the memory function be utilized,then none of the members need be transparent to light.

Except for being nonconductive or good insulators g mustbe'smoothand-havea dielectric "breakdown volt- 5 age of about 10 00%." andbeelectrically homogeneous on aimicroscopic scale (-e.g., no cracks,bubbles, cry'stals, dirt sui'face films, etc). ,In addition, thesurfaces the electrical properties of support members 16jandf1- are notcritical. The main function of supportmembers 16 and 17 is to provide 1mechanical support and f strength for the entire panel, particulariywit'h '.respect to pressure differential acting on .thep'aneland'therrnal" shock. As noted earlier, theyshojuld have thermal ete,pansion characteristics substantially matching the ther mal expansioncharacteristics 'of dielectric layers 10 6 dielectric coatings 10 and11. For given pressure differentials and thickness of plates, the stressand deflection of plates may be determined] by following standard stressand strain formulas (see R. J. Roark, Formulas for Stress and Strain,McGraw-Hill, 1954).

Spacer 15 may be made of the same glass material as dielectric films 10and 11 and may be an integral rib formed on one of the dielectricmembers and fused to the other members to form a bakeable hermetic sealenclosing and confining the ionizable gas volume 12. However, a separatefinal hermetic seal may be effected by a high strength devitrified glasssealant 15S.

Tubulation 18 is provided for exhausting the space between dielectricmembers 10 and 11 and filling that space with the volume of ionizablegas. For large panels small beadlike solder glass spacers such as shownat 1513 may be located between conductor intersections and fused todielectric members 10 and 11 to aid in withstanding stress on the paneland maintain uniformity of thickness of gas volume 12. 7

Conductor arrays 13 and 14 may be formed on support members 16 and 17 bya number of well-known processes, such as photoetching, vacuumdeposition, stencil screening, etc. In the panel shown in FIG. 4, theceriter-to-center spacing of conductors in the respective arrays isabout 17 mils. Transparent or semi-transparent conductive material suchas tin oxide, gold, or

aluminum can be used to form the conductor arrays and should have aresistance less than 3000 ohms per line. Narrow opaque electrodes mayalternately be uses so that discharge light passes around the edges ofthe electrodes to the viewer. It is important to select a conductormaterial that is not attacked during processing by the dielectricmaterial.

It will be appreciated that conductor arrays 13 and 14 may be wires orfilaments of copper, gold, silver or aluminum or any other conductivemetal or material. For example 1 mil wire filaments are commerciallyavailable and may be used in the. invention. However, formed in situconductor arrays are preferred since they may be more easily anduniformly placed onand adhered to the support plates 16 and 17,

Dielectric layer members 10 an'd ll are formed of an such material isasolder glass such as I(imble SG'-68 manufactured by and commerciallyavailable from the assignee of the present invention. i

This galss has thermal expansion characteristics substantially matchingthe thermal expansion characteristics of certain so(la-limeglasseawand"can be used as the dielectric layer wherifthe 'supportmembers 1:6arid' 17 aresodalimejglas's plates'iflielectric layers {10and 1.1

of dielectric layers 10 and '11 should be good photo- "emi'tters ofelectrons in a baked out condition. Alter- "nately, dielectric'layers 10and .11 may be overcoated with materials designed to produce goodelectron emisand 11. Ordinary inch commercial 'grade soda lime sion, asin US. letters Pat. No. 3,634,719, issued to Roger E. Ernsthausen. Ofcourse, for an optical display at least one of dielectric layers 10 and11 should pass light generated on discharge and be transparent ortranslucent and, preferably, both layers are optically transparent.

The preferred spacing between surfaces of the dielectric films is about4 to 8 mils with conductor arrays 13 and 14 having center-to-centerspacing of about 17 mils.

The ends of conductors 14-1 14-4 and support member 17 extend beyond theenclosed gas volume 12 and are exposed for the purpose of makingelectrical connection to interface and addressing circuitry 19.Likewise, the ends of conductors 13-1 13-4 on support member 16 extendbeyond the enclosed gas volume l2 and are exposed for the purpose ofmaking electrical connection to interface and addressing circuitry 19.

As in known display systems, the interface and addressing circuitry orsystem 19 may be relatively inexpensive line scan systems or thesomewhat more expensive high speed random access system. In either case,it is to be noted that a lower amplitude of operating potentials helpsto reduce problems associated with the interface circuitry between theaddressing system and the display/memory panel, per se. Thus, byproviding a panel having greater uniformity in the dischargecharacteristics throughout the panel, tolerances and operatingcharacteristics of the panel with which the interfacing circuitrycooperate, are made less rigid.

One mode of initiating operation of the panel will be described withreference to FIG. 3, which illustrates the condition of one elementalgas volume 30 having an elemental cross-sectional area and volume whichis quite small relative to the entire volume and cross-sectional area ofgas 12. The cross-sectional area of volume 30 is defined by theoverlapping common elemental areas of the conductor arrays and thevolume is equal to the product of the distance between the dielectricsurfaces and the elemental area. It is apparent that if the conductorarrays are uniform and linear and are orthogonally (at right angles toeach other) related each of elemental areas X and Y will be squares andif conductors of one conductor array are wider than conductors of theother conductor arrays, said areas will be rectangles. If the conductorarrays are at transverse angles relative to each other, other than 90,the areas will be diamond shaped so that the cross-sectional shape ofeach volume is determined solely in the first instance by the shape ofthe common area of overlap between conductors in the conductor arrays 13and 14. The dotted lines 30' are imaginary lines to show a boundary ofone elemental volume about the center of which each elemental dischargetakes place. As described earlier herein, it is known that thecross-sectional area of the discharge in a gas is affected by, interalia, the pressure of the gas, such that, if desired, the discharge mayeven be constricted to within an area smaller than the area of conductoroverlap. By utilization of this phenomena, the light production may beconfined or resolved substantially to the area of the elementalcross-sectional area defined by conductor overlap. Moreover, byoperating at such pressure charges (ions and electrons) produced ondischarge. are laterally confined so as to not materially affectoperation of adjacent elemental discharge volumes.

In the instant shown in FIG. 3, a conditioning discharge about thecenter of elemental volume 30 has been initiated by application toconductor 13-1 and conductor 14-1 firing potential V,, as derived from asource 35 of variable phase, for example, and source 36 of sustainingpotential V, (which may be a sine wave, for example). The potential V,is added to the sustaining potential V,- as sustaining potential Vincreases in magnitude to initiate the conditioning discharge about thecenter of elemental volume 30 shown in FIG. 3. There, the phase of thesource 35 of potential V, has been adjusted into adding relation to thealternating voltage from the source 36 of sustaining voltage V,- toprovide a voltage V;', when switch 33 has been closed, to conductors13-1 and 14-1 defining elementary gas volume 30 sufficient (in timeand/or magnitude) to produce a light generating discharge centered aboutdiscrete elemental gas volume 30. At the instant shown, since conductor13-1 is positive, electrons 32 have collected on and are moving to anelemental area of dielectric member 10 substantially corresponding tothe area of elemental gas volume 30 and the less mobile positive ions 31are beginning to collect on the opposed elemental area of dielectricmember 11 since it is negative. As these charges build up, theyconstitute a back voltage opposed to the voltage applied to conductors13-1 and 14-1 and serve to terminate the discharge in elemental gasvolume 30 for the remainder of a half cycle.

During the discharge about the center of elemental gas volume 30,photons are produced which are free to move or pass through gas medium12, as indicated by arrows 37, to strike or impact remote surface areasof photoemissive dielectric members 10 and 11, causing such remote areasto release electrons 38. Electrons 38 are, in effect, free electrons ingas medium 12 and condition each other discrete elemental gas volume foroperation at a lower firing potential V; which is lower in magnitudethan the firing potential V, for the initial discharge about the centerof elemental volume 30 and this voltage is substantially uniform foreach other elemental gas volume.

Thus, elimination of physical obstructions or barriers between discreteelemental volumes, permits photons to travel via the space occupied bythe gas medium 12 to impact remote surface areas of dielectric members10 and 11 and provides a mechanism for supplying free electrons to allelemental gas volumes, thereby conditioning all discrete elemental gasvolumes for subsequent discharges, respectively, at a uniform lowerapplied potential. While in FIG. 3 a single elemental volume 30 isshown, it will be appreciated that an entire row (or column) ofelemental gas volumes may be maintained in a tired condition duringnormal operation of the device with the light produced thereby beingmasked or blocked off from the normal viewing area and not used fordisplay purposes. It can be expected that in some applications therewill always be at least one elemental volume in a fired condition andproducing light in a panel, and in such applications it is not necessaryto provide separate discharge or generation of photons for purposesdescribed earlier.

However, as described earlier, the entire gas volume can be conditionedfor operation at uniform firing potentials by use of external orinternal radiation so that there will be no need for a separate sourceof higher potential for initiating an initial discharge. Thus, byradiating the panel with ultraviolet radiation or by inclusion of aradioactive material within the glass materials or gas space, alldischarge volumes can be operated at uniform potentials from addressingand interface circuit 19.

Since each discharge is terminated upon a build up or storage of chargesat opposed pairs of elemental areas, the light produced is likewiseterminated. In fact, light 9 production lasts for only a small fractionof a half cycle of apllied alternating potential and depending on designparameters, is in the nanosecond range.

After the initial firing or discharge of discrete elemental gas volume30 by a firing potential V,', switch 33 may be opened so that only thesustaining voltage V from source 36 is applied to conductors 13-1 and14-1. Due to the storage of charges (e.g., the memory) at the opposedelemental areas X and Y, the elemental gas volume 30 will dischargeagain at or near the peak of negative half cycles of sustaining voltageV to again produce a momentary pulse of light. At this time, due toreversal of field direction, electrons 32 will collect on and be storedon elemental surface area Y of dielectric member 11 and positive ions 31will collect and be stored on elemental surface area X of dielectricmember 10. After a few cycles of sustaining voltage V,, the times ofdischarges become symmetrically located with respect to the wave form ofsustaining V,,. At remote elemental volumes, as for example, theelemental volumes defined by conductor 14-1 with conductors 13-2 and13-3, a uniform magnitude or potential V, from source 60 is selectivelyadded by one or both of switches 34-2 or 34-3 to the sustaining voltageV,, shown as 36, to fire one or both of these elemental dischargevolumes. Due to the presence of free electrons produced as a result ofthe discharge centered about elemental volume 30, each of these remotediscrete elemental volumes have been conditioned for operation atuniform firing potential V;.

In order to turn of an elemental gas volume (i.e., terminate a sequenceof discharge representing the on state), the sustaining voltage may beremoved. However, since this would also turn of other elemental volumesalong a row or column, it is preferred that the volumes be selectivelyturned of by application to selected on elemental volumes a voltagewhich can neutralize the charges stored at the pairs of opposedelemental areas.

This can be accomplished in a number of ways, as for example, varyingthe phase or time position of the potential from source 60 to where thatvoltage combined with the potential from source 36 falls substantiallybelow the sustaining voltage.

It is apparent that the plates 16-17 need not be flat but may be curved,curvature of facing surfaces of each plate being complementary to eachother. While the preferred conductor arrangement is of the crossed gridtype as shown herein, it is likewise apparent that where an infinitevariety of two dimensional display patterns are not necessary, as wherespecific standardized visual shapes (e.g., numerals, letters, words,etc.) are to be formed and image resolution is not critical, theconductors may be shaped accordingly. Reference is made to British Pat.Specification No. 1,302,148 and U.S. letters Pat. No. 3,71 1,733 whereinnon-grid electrode arrangements are illustrated.

The device shown in FIG. 4 is a panel having a large number of elementalvolumes similar to elemental volume 30 (FIG. 3). In this case more roomis provided to make electrical connection to the conductor arrays 13'and 14', respectively, by extending the surfaces of support members 16and 17' beyond seal 15S, alternate conductors being extended onalternate sides. Conductor arrays 13 and 14' as well as support members16' and 17' are transparent. The dielectric coatings are not shown inFIG. 4 but are likewise transparent so that the panel may be viewed fromeither side.

THE INVENTION In accordance with the practice of this invention, thereis provided a gaseous discharge display/memory device having chargestorage members, each of which comprises at least one thin continuousdielectric film having a minimum thickness sufficient to store chargeswithout breaking down or otherwise deteriorating upon gas discharge dueto thermal, physical, electrical, or other operation originated stressesand having a maximum thickness less than that thickness where the filmbecomes discontinuous due to breakdown caused by deposition originatedstresses.

In the practice hereof, it is contemplated that the dielectric thicknessmay typically range from about 250 angstrom units up to about 150,000angstrom units, preferably about 10,000 angstrom units up to about100,000 angstrom units.

The thin dielectric film may comprise a single layer or a combination oftwo or more layers, each layer being of the same or differentcomposition.

In the broad practice hereof, it is contemplated using a thin dielectricfilm comprised of one or more layers selected from any suitable metal ormetalloid compound, particularly oxides.

It is especially contemplated using oxides of Al, Ti, Zr, Hf, Si, Pb, orGroupa IIA (Be, Mg, Ca, Sr, Ba, or Ra).

One specific combination contemplated herein comprises a first layer ofsilicon oxide having a thickness of about 10,000 angstrom units to about70,000 angstrom units, a second layer of aluminum oxide having athickness of about angstrom units to about 2,000 angstrom units, and athird (or top) layer of lead oxide having a thickness of about I00angstrom units to about 2,000 angstrom units.

Another specific combination includes a first layer of about 10,000angstrom units to about 70,000 angstrom units of silicon oxide and asecond layer of about 100 angstrom units to about 2,000 angstrom unitsof lead oxide.

Another specific combination includes a first layer of about 10,000angstrom units to about 70,000 angstrom units of silicon oxide and about100 angstrom units to about 2,000 angstrom units of magnesium oxide.

Another specific combination includes a first layer of about l0,000angstrom units to about 70,000 angstrom units of silicon oxide, about100 angstrom units to about 2,000 angstrom units of aluminum oxide, andabout 100 angstrom units to about 2,000 angstrom units of magnesiumoxide.

Another specific combination includes a first layer of about 10,000angstrom units to about 125,000 angstrom units of aluminum oxide and asecond layer of about 100 angstrom units to about 2,000 angstrom unitsof lead oxide.

Another specific combination includes a first layer of about 10,000angstrom units to about 125,000 angstrom units of aluminum oxide and asecond layer of about 100 angstrom units to about 2,000 angstrom unitsof magnesium oxide. I

Another specific combination includes a first layer of about 10,000angstrom units to about 40,000 angstom units of magnesium oxide, about40,000 angstrom units to about 90,000 angstrom units of aluminum oxide,and about 100 angstrom units to about 2,000 angstrom units of leadoxide.

In addition, one or more dielectric layers may be of an electronemissive substance, as discussed in copending U.S. Pat. application Ser.No. 67,604, filed Aug. 27, 1970, and owned by the same assignee of theinstant application.

It may be especially useful to use an electron emissive substance as thetop layer in the dielectric, e.g., with a thickness of about 100angstrom units to about 2,000 angstrom units. Typical electron emissivematerials include not by way of limitation Group IA elements, Group IAoxides, GaAs, GaP, InAs, InSb, InP, NiO, CsF, Csl, AgOCs, and AuOCs. Useof Csl has resulted in substantially lower operating voltages in a gasdischarge device.

As used herein the terms film" or layer" are intended to be allinclusive of other similar terms such as deposit, coatingfinish, spread,covering, etc.

It is contemplated that each dielectric oxide layer may be applieddirectly to the supporting substrate or formed in situ thereon.

Typical means of applying a dielectric layer directly to a supportingsubstrate include not by way of limitation vapor deposition; vacuumdeposition; chemical vapor deposition; wet spraying upon the surface amixture or solution of the dielectric composition suspended or dissolvedin a liquid followed by evaporation of the liquid; dry spraying of thedielectric composition; electron beam evaporation; plasma flame and/orare spraying and/or deposition; ion plating; and sputtering targettechniques. Likewise, combinations of such techniques may be used.

In situ processes include applying a metal or metalloid (or sourcethereof) to the supporting substrate and then oxidizing the appliedmaterial. The applying of the metal, metalloid, or source thereof may beby any convenient means, such as discussed hereinbefore vapordepositionyvacuum deposition, etc.

One specific in situ process comprises applying metal or metalloid meltfollowed by oxidation of the melt during the cooling thereof so as toform the oxide layer.

Another in situ process comprises an oxidizable source I of theelemental metal'or metalloid to the surface. Typical of such oxidizablesources include minerals and/or compounds containing the metal ormetalloid, especially those organometals or organometalloids which arereadily heat decomposed or pyrolyzed.

One of the advantages of this invention is that the thin dielectriclayer or multi-layer is applied directly over the electrode array, thussubstantially reducing the relatively high economic cost inherent in asocalled thick-film process. Likewise, the practice of this invention isessentially a cold process, relative to a thick-film process, since thinfilms may typically be applied at lower temperatures. The use of lowertemperatures has the further advantage of reducing the number ofelectrode breaks and substrate warping.

Although this invention has been primarily described hereinbefore withreference to thin dielectric oxide compositions, other metal ormetalloid compounds may be utilized, especially the halides such as MgFBeF CaF NaCl, etc. Likewise, glass or ceramic compositions may beutilized, especially the dolomitic aluminosilicates, borosilicates, leadsilicates, and lead borosilicates. Y I

In FIG. 5, there is shown substrates 16, 17, gaseous medium 12,electrodes 13, 14, and thin dielectric layers 100, 110.

In FIG. 6, there is shown substrates 16, 17, gaseous medium 12,electrodes 13, 14, thin dielectric layers 200, 210, and dielectricovercoats 201, 211.

In FIG. 7, there is shown substrates 16, 17, gaseous medium 12,electrodes l3, l4, thin dielectric layers 300, 310, first overcoats 301,311, and second overcoats 302, 312.

We claim:

1. In a gaseous discharge display/memory device comprising an ionizablegaseous medium in a sealed gas chamber formed by a pair of opposedcharge storage members backed by electrode members, the improvementwherein at least one charge storage member, consisting of at least twothin continuous dielectric layers, has a minimum thickness sufficient tostore charges without deteriorating upon gas discharge and a maximumthickness less than that thickness at which the charge storage memberbecomes discontinuous due to breakdown caused by deposition originatedstresses, said charge storage member comprising a first layer of about10,000 angstrom units to about 125,000 angstrom units of aluminum oxideand a second layer of about angstrom units to about 2000 angstrom unitsof a member selected from the group consisting of lead oxide andmagnesium oxide.

1. IN A GASEOUS DISCHARGE DISPLAY/MEMORY DEVICE COMPRISING AN IONIZABLEGASEOUS MEDIUM IN A SEALED GAS CHAMBER FORMED BY A PAIR OF OPPOSEDCHARGE STORAGE MEMBERS BACKED BY ELECTRODE MEMBERS, THE IMPROVEMENTWHEREIN AT LEAST ONE CHARGE STORAGE MEMBER, CONSISTING OF AT LEAST TWOTHIN CONTINUOUS DIELECTRIC LAYERS, HAS A MINIMUM THICKNESS SUFFICIENT TOSTORE CHARGES WITHOUT DETERIORATING UPON GAS DISCHARGE AND A MAXIMUMTHICKNESS LESS THAN THAT THICKNESS AT WHICH THE CHARGE STORAGE MEMBERBECOMES DISCONTINUOUS DUE TO BREAKDOWN CAUSED BY DEPOSITION ORIGINATEDSTRESSES, SAID CHARGE STORAGE MEMBER COMPRISING A FIRST LAYER OF ABOUT10,000 ANGSTRON UNITS TO ABOUT 125,000 ANGSTROM UNITS OF ALUMINUM OXIDEAND A SECOND LAYER OF ABOUT 100 ANGSTROM UNITS TO ABOUT 2000 ANGSTROMUNITS OF A MEMBER SELECTED FROM THE GROUP CONSISTING OF LEAD OXIDE ANDMAGNESIUM OXIDE.